Pediatric urogenital schistosomiasis diagnosed in France

BACKGROUND

Schistosomiasis affects approximately 230 million people worldwide. There is an increased incidence of schistosomiasis cases in France acquired from outside the country. This increases the risk of schistosomiasis outbreaks as observed in Corsica. Clinicians from non-endemic regions are not accustomed to diagnosing and managing this pathology. The objective of this study is to provide a better description of the clinical and paraclinical characteristics and disease evolution of affected children.

METHODS

Through the French Pediatric Nephrology Society and the Pediatric Infectious Pathology Group, we contacted all French pediatric centers that may have treated children with urinary schistosomiasis between 2013 and 2019. Age, sex, comorbidities, and clinical, biological, and radiological data (at discovery and follow-up) were collected retrospectively.

RESULTS

A total of 122 patients from 10 different centers were included. The median age was 14 years and the sex ratio M/F was 4:1. Hematuria was present in 82% of the patients while urinary tract abnormality was found in 36% of them. Fourteen patients (11%) displayed complicated forms of urinary schistosomiasis including 10 patients with chronic kidney disease. A total of 110 patients received treatment with praziquantel, which was well-tolerated and led to clinical resolution of symptoms in 98% of cases.

CONCLUSION

Patients with schistosomiasis present frequent kidney, urinary, or genital involvement. Systematic screening of patients returning from endemic areas is therefore recommended, especially since treatment with antiparasitic drugs is effective and well-tolerated. Enhancing medical knowledge of this pathology among all practitioners is essential to improve care and outcomes.

Differences and similarities between Monkeypox and Chickenpox in children during an outbreak

INTRODUCTION

Herein, we described cases of children under 16 years old suspected to be infected with Monkeypox virus (MKPV) and diagnosed with chickenpox in public hospitals of Marseille, south of France.

MATERIAL AND METHODS

We conducted a retrospective study from March 23rd, 2022 to October 20th, 2022 in our institution of results of MKPV DNA and varicella-zoster virus (VZV) DNA detection by PCR performed on cutaneous lesions swabs collected from children <16 years old.

RESULTS

None of the cutaneous swabs collected from 14 children were positive for MKPV DNA. In contrast, 30/168 (17 %) cutaneous swabs collected from children were positive for VZV DNA. Of these 30 VZV-positive children, 7 had been suspected of MKPV infection because of their atypical rash, due to the location of the lesions and the chronology of their appearance.

DISCUSSION

As in our cohort, pediatric cases of the 2022 Monkeypox outbreak in non-endemic developed countries have been very rare. This variant of MKPV does not normally spread easily and requires very close physical contact between an infected person (skin lesions, bodily fluids or respiratory droplets) and another person to be transmitted. It will nevertheless be a question of remaining vigilant as not to ignore the possibility of close contact or sexual transmission of Monkeypox in a child, or the possibility of a new and more contagious variant.

CONCLUSION

It is difficult to differentiate Monkeypox infection from other infections associated with rashes, it is important to remember that viruses change as well as their forms of presentation.

Development of a 3D ultrafast laser written near-infrared spectro-interferometer

Direct ultrafast laser photoinscription of transparent materials is a powerful technique for the development of embedded 3D photonics. This is particularly adaptable for astrophotonic devices when a number of inputs are required. The process relies essentially on volume fabrication of waveguiding structures in flexible 3D designs and refractive index contrast parameters adjustable for specific spectral ranges. This enables 3D geometry and thus avoids in-plane crossings of waveguides that can induce losses and cross talk in multi-telescope beam combiners. The additional novel capability of the technique allows for the fabrication of high aspect ratio nanostructures nonperturbatively sampling the optical field. Combining ultrafast laser micro- and nanoprocessing with engineered beams, we present here results for the development of chip-sized silica glass integrated robust 3D three-telescope beam combiners in the near-IR range, as well as embedded diffraction gratings, for phase closure analysis and spectro-interferometry applications in astronomy.

Waveguide scattering antennas made by direct laser writing in bulk glass for spectrometry applications in the short-wave IR

A buried straight waveguide perturbed periodically by six antennas composed of submicronic cylinder voids is entirely fabricated using ultrafast laser photoinscription. The light scattered from each antenna is oriented vertically and is detected by a short-wave IR camera bonded to the surface of the glass with no relay optics. The response of each antenna is analyzed using a wavelength tunable laser source and compared to simulated responses verifying the behavior of the antenna. These results show the good potential of the direct laser writing technique to realize monolithic embedded detectors by combining complex optical functions within a 3D design. A wavelength meter application with a spectral resolution of 150 pm is proposed to demonstrate this combination.

Systematic Endotracheal Aspiration in the Pediatric Intensive Care Unit Reduces Broad-spectrum Antibiotic Use for Ventilator-associated Pneumonia

AIM

To determine the impact of a systematic endotracheal aspiration (ETA) sampling program for mechanically ventilated patients on initial antibiotic therapy for ventilator-acquired pneumonia (VAP).

DESIGN

Retrospective cohort study; before-after study design.

SETTING

Pediatric intensive care unit (PICU) with 16 medical and surgical beds in a tertiary teaching hospital.

SUBJECTS

Patients <16 years of age hospitalized in the PICU who fulfilled VAP criteria.

INTERVENTION

Biweekly systematic ETA sampling was conducted in mechanically ventilated patients.

MEASUREMENTS

We retrospectively studied patients who received antibiotic therapy for suspected VAP 12 months before and after the initiation of systematic ETA (periods 1 and 2, respectively), evaluating the initial antibiotic therapy spectrum in both periods.

RESULTS

During period 1, 56 patients developed VAP and 47 developed VAP during period 2. The incidence was 17 cases of VAP/1000 days of mechanical ventilation in both periods. Ideal antibiotic therapy was prescribed in 19.6% of cases for period 1 and 55.2% for period 2 (P = 0.001). Initial antibiotic therapy for VAP during period 2 had a significantly lower proportion of broad-spectrum antibiotics than therapy during period 1 (P = 0.01).

CONCLUSION

In our PICU, knowledge of bronchial colonization reduced initial broad-spectrum antibiotic use for VAP.

Real-life requests for Bordetella polymerase chain reaction testing in children presenting to hospital

From 2015 to 2017, 3197 interpretable Bordetella polymerase chain reaction (PCR) tests were performed for 2760 children presenting to our tertiary university hospital. Requests mainly came from the emergency department (62%) and for children older than 1 year (68%). Only 32 PCR (1%) results were positive, mainly in children younger than 1 year (n = 29/32, 90.6%; p<0.001). When focusing on the PCR indications in 2017, we found the requests were mainly based on nonspecific respiratory symptoms and were clinically unjustified in 383 cases (39%). Pediatricians overused Bordetella PCR in clinical practice. They should reserve their requests for cases of young children with symptoms suggestive of respiratory illness and/or incomplete pertussis immunization.

Noncontiguous finished genome sequences and descriptions of Actinomyces ihuae, Actinomyces bouchesdurhonensis, Actinomyces urinae, Actinomyces marseillensis, Actinomyces mediterranea and Actinomyces oralis sp. nov. identified by culturomics

The taxonogenomic approach, including the culturomics techniques, is now currently used to isolate and characterize new bacteria. These approaches notably allowed us to discover six new species of the Actinomyces genus: Actinomyces ihuae strain SD1, Actinomyces bouchesdurhonensis strain Marseille-P2825, Actinomyces urinae strain Marseille-P2225, Actinomyces marseillensis strain Marseille-P2818, Actinomyces mediterranea strain Marseille-P3257 and Actinomyces oralis strain Marseille-P3109. Each is the type strain of the corresponding bacterial species. 16S ribosomal RNA gene sequence comparison was used to classify these strains among the Actinomyces genus. These strains are all Gram positive, rod shaped and facultative aerobic. We describe the main characteristics of each bacterium and present their complete genome sequence and annotation.

[Pseudomonas aeruginosa in dermatology]

Pseudomonas aeruginosa, a ubiquitous Gram-negative bacillus characterized by its greenish color and sweetish smell, is at the origin of potentially severe forms of dermatosis, such as ecthyma gangrenosum which marks immunosuppression or reveals blood-poisoning, especially in children. It frequently colonizes chronic wounds and serious burns, and spongiotic or acantholytic dermatosis, especially when severe or localized in skinfolds. It requires special care because of its high resistance to antibiotics and antiseptics. It can also involve folliculitis favored by water sports or a nail disorder (chloronychia).

'Arcanobacterium urinimassiliense' sp. nov., a new bacterium isolated from the urogenital tract

Herein we report the main characteristics of ‘Arcanobacterium urinimassiliense’ strain Marseille-P3248^T (=CSUR P3248) isolated from a urine sample of a 54-day-old girl with rotavirus gastroenteritis.

'Bacteroides ihuae' sp. nov., a new bacterial species isolated from the human respiratory microbiome

We present the main features of ‘Bacteroides ihuae’ sp. nov., strain Marseille-P2824^T (CSUR P2824), isolated from the sputum of healthy Frenchwoman living in Marseille.

Review of poxvirus: emergence of monkeypox

This article reviews the different types of poxvirus infections. Smallpox, although eradicated, must continue to be monitored because of the potential risk of accidental or voluntary (by bioterrorism) reintroduction. Monkeypox and cowpox viruses are considered to be emergent today ; their high risk of dissemination is due to the increase in international transport as well as trends for new animals as pets and the loss of vaccinal protection against smallpox. Molluscum contagiosum (molluscipoxvirus) causes mild infections, is particularly frequent in children ; in adults it is a marker of the risk of sexually transmitted infections and can, in cases with profuse lesions, reveal AIDS.

"Corynebacterium urinapleomorphum" sp. nov., isolated from a urine sample of a 2-month-old boy affected by rotavirus gastroenteritis

We report the main characteristics of "Corynebacterium urinapleomorphum" strain Marseille-P2799^T (CSURP2799), isolated from a urine sample from a 2-month-old boy with rotavirus gastroenteritis.

‘Urinacoccus massiliensis’ gen. nov. sp. nov., identified in urine sample of a 7-year-old boy hospitalized for dental care under general anaesthesia

We report here the main characteristics of ‘Urinacoccus massiliensis’ gen. nov. sp. nov., strain FC2 (CSURP1992). This strain was isolated from the urine of an asymptomatic 7-year-old boy.

Anaerococcus urinomassiliensis sp. nov., isolated from a urine sample of a 17-year-old boy affected by autoimmune hepatitis and membranoproliferative glomerulonephritis

We report the main characteristics of ‘Anaerococcus urinomassiliensis’ strain FC4^T (CSURP2143) that was isolated from a urine sample of a 17-year-old boy affected by autoimmune hepatitis and membranoproliferative glomerulonephritis.

Actinomyces urinae sp. nov., isolated from 13-year-old girl affected by nephritic syndrome

Here, we report the main characteristics of Actinomyces urinae strain Marseille-P2225^T (CSURP2225) isolated from a human urine sample.

High Q whispering gallery modes in GaAs/AlAs pillar microcavities

We report the observation of whispering gallery modes (WGM) in high quality GaAs/AlAs pillar microcavities defined by electron-beam lithography and electron cyclotron resonance reactive ion etching. Photoluminescence experiments, conducted using InAs quantum dots as an internal probe, reveal a remarkably simple WGM spectrum, consisting of a single series of TE modes. For diameters ranging from 3 to 4 mum, Q-factors in excess of 15 000 were measured, allowing for WGM lasing. Noticeably, sub-micron diameter micropillars also display high Qs (~ 1000), close to the limit set by intrinsic radiative losses. These results open the way to the development of original microlasers and improved quantum-dot single photon sources.

[Properties of a cephalosporinase produced by Proteus penneri inhibited by clavulanic acid]

P. penneri produces an inducible cephalosporinase, as many Enterobacteriaceae. Nevertheless this betalactamase is susceptible to clavulanic acid which is an exception also encountered for P. vulgaris. The authors studied the enzyme produced by P. penneri 14HBC resistant to cefotaxime (MIC 16 mg/l) isolated in Spain in 1992. This betalactamase of isoelectric point 6.65 hydrolyzes first generation cephalosporins, amoxycillin and poorly ticarcillin as it occurs for all cephalosporinases. However, this enzyme hydrolyzes strongly oxyimino-cephalosporins: cefuroxime, cefotaxime, cefepime, cefpirome as it occurs with extended-spectrum betalactamases. Cephamycins and imipenem are not substrates. Clavulanic acid has a very good affinity for this betalactamase which is inactivated progressively. These properties are similar to those of the enzyme of P. vulgaris Ro104 of isoelectric point 8.3 which, contrarily to other cephalosporinases, belongs to the structural Ambler's class A.

Interactions of ceftibuten with extended-spectrum beta-lactamases: a bacteriological and enzymatic analysis

The authors analysed the antibacterial activity of ceftibuten, cefotaxime, ceftazidime and aztreonam against Klebsiella pneumoniae strains, including those which produced novel extended-spectrum beta-lactamases. These molecules were also tested for their susceptibility to cell-free extracts of the corresponding beta-lactamases. Both approaches showed that ceftibuten was not hydrolysed by the CTX-1/TEM-3, SHV-2 and SHV-3 beta-lactamases, while cefotaxime, ceftazidime and aztreonam were hydrolysed. Nevertheless all compounds were substrates for the SHV-4 and SHV-5 beta-lactamases, and the organisms which produced these beta-lactamases showed increased MICs.

Multiplicity of TEM-derived beta-lactamases from Klebsiella pneumoniae strains isolated at the same hospital and relationships between the responsible plasmids

Five plasmid-mediated beta-lactamases conferring high-level resistance to ceftazidime were isolated from Klebsiella pneumoniae strains in the same hospital. These enzymes had isoelectric points ranging from 5.3 to 6.5 (CAZ-1, 5.55; CAZ-2, 6.0; CAZ-3, 5.3; CAZ-6, 6.5; and CAZ-7, 6.3). All isolates and their Escherichia coli transconjugants were highly resistant to amoxicillin (MICs, greater than 4,096 micrograms/ml), piperacillin (64 to 256 micrograms/ml), cephalothin (32 to 256 micrograms/ml), and ceftazidime (32 to 512 micrograms/ml) but remained moderately susceptible to cefotaxime (0.5 to 8 micrograms/ml). Only CAZ-6- and CAZ-7-producing strains were highly resistant to aztreonam (64 to 128 micrograms/ml). All the isolates remained susceptible to moxalactam and imipenem. The reduced activity of piperacillin, cefotaxime, ceftazidime, or aztreonam was restored by 2 micrograms of clavulanate, sulbactam, tazobactam, or brobactam per ml for E. coli producing CAZ-2, CAZ-3, and CAZ-7. Sulbactam had a lower protective effect than other inhibitors for E. coli harboring CAZ-1 and especially CAZ-6. Except for CAZ-1, which was mediated by a 150-kilobase (kb) plasmid (pCFF14), the other ceftazidimases were mediated by plasmids of 85 kb with EcoRI digestion patterns similar to that of pCFF04 encoding CTX-1 beta-lactamase. A TEM probe hybridized with a 19-kb EcoRI fragment of all these closely related plasmids.

Interactions of meropenem, with beta-lactamases, including enzymes with extended-spectrum activity against third-generation cephalosporins

The interactions of a meropenem were studied with a set of beta-lactamases including the new TEM- and SHV-related plasmid-mediated enzymes that have extended-spectrum activity against third-generation cephalosporins ('cefotaximases' and 'ceftazidimases'). Meropenem and imipenem were highly resistant to the hydrolytic activity of all the TEM and SHV related beta-lactamases, and to the OXA enzymes, as were the cephamycins: cefoxitin and cefotetan. The two carbapenems were also highly stable to Class C beta-lactamases (chromosomal cephalosporinases) whereas third-generation cephalosporins and cephamycins were slowly hydrolyzed. Both carbapenems demonstrated quite similar affinities for all the enzymes studied. In some instances, and particularly with Class A (TEM- and SHV-derived) enzymes, meropenem inactivated the beta-lactamase activity. Imipenem appeared less reactive in this respect.

Comparative study of a novel plasmid-mediated beta-lactamase, CAZ-2, and the CTX-1 and CAZ-1 enzymes conferring resistance to broad-spectrum cephalosporins

Infections caused by strains of Klebsiella pneumoniae resistant to broad-spectrum cephalosporins have been observed recently in hospitals in Clermont-Ferrand, France. beta-Lactam resistance resulted primarily from the plasmid-mediated, expanded-spectrum CTX-1 beta-lactamase. Furthermore, since 1987 some K. pneumoniae isolates more resistant to ceftazidime than to other cephalosporins have been observed. This new resistance phenotype was the result of the production of ceftazidimase CAZ-1 and, more recently, CAZ-2. As in CTX-1-producing strains, resistance to beta-lactams resulting from CAZ-2 was associated with resistance to aminoglycosides except gentamicin, sulfonamide, and tetracycline and was transferable to Escherichia coli by conjugation. Agarose gel electrophoresis of plasmid DNA from wild-type strains and transconjugants indicated that CAZ-2 production was mediated by a plasmid of 85 kilobases highly related to plasmid pCFF04 coding for CTX-1 beta-lactamase. The isoelectric point, close to 6.0, of this novel enzyme differed from those of CTX-1 and CAZ-1. Like CAZ-1, the CAZ-2 enzyme efficiently hydrolyzed ceftazidime and aztreonam, but as with CTX-1, cefotaxime gave the maximal reaction rate. For each expanded-spectrum beta-lactamase, the activity of broad-spectrum cephalosporins was restored by clavulanic acid or sulbactam.

[Behavior of ceftazidime in regard to different classes of beta-lactamases. The situation in 1988]

Following Ambler's observations, B-lactamases can be divided in four classes, probably derived from a very small number of ancestral genes. Class A includes the TEM-type beta-lactamases (TEM-1, TEM-2), PIT-2/SHV-1 and others which do not hydrolyse ceftazidime and other third-generation cephalosporins. The new plasmid-mediated beta-lactamases markedly active against third-generation cephalosporins also belong to class A and the primary structures of few of them are known. All the class A beta-lactamases are highly susceptible to the action of beta-lactamase inhibitors: clavulanic acid, sulbactam, YTR-830, and are devoid of any hydrolytic properties for cephamycins and imipenem. Third-generation cephalosporins are slowly hydrolyzed by the class C beta-lactamases: the inducible cephalosporinases. Thus only organisms which produce derepressed cephalosporinases are resistant to third-generation cephalosporins, but individual variations are known.

Interactions of new plasmid-mediated beta-lactamases with third-generation cephalosporins

The kinetic constants of three recently identified plasmid-mediated beta-lactamases--SHV-2, CTX-1, and CAZ-1--markedly active against third-generation cephalosporins were analyzed in comparison with three better-characterized beta-lactamases--two plasmid-mediated enzymes, TEM-2 and PIT-2/SHV-1, and R-30, a beta-lactamase from Klebsiella oxytoca that has few similarities to the newer enzymes. All of these enzymes are synthesized constitutively, demonstrate efficient hydrolysis of penicillins, are highly susceptible to the action of clavulanic acid and sulbactam, and have no detectable activity against the cephamycins and imipenem. With the methoxyimino cephalosporins, including those of the third generation, the rates of hydrolysis observed for the SHV-2, CTX-1, and CAZ-1 enzymes are high and show no relation to those observed for the other presently known beta-lactamases. Structure-activity relations suggest that the oxime substituent of these cephalosporins is a major structural factor in the catalytic process observed with the three new beta-lactamases.

Kinetic properties of two plasmid-mediated beta-lactamases from Klebsiella pneumoniae with strong activity against third-generation cephalosporins

We determined the kinetic constants for two plasmid-mediated beta-lactamases with strong activity against third-generation cephalosporins: CTX-1 and SHV-2. The enzymes had many similar properties: their synthesis was constitutive and they were significantly active against penicillins as well as cephalosporins. The two enzymes thus differed considerably from the chromosomal cephalosporinases, but bore some resemblance to the commonly-encountered plasmid-coded penicillinases, such as TEM beta-lactamases. Moreover, like the TEM enzymes, the plasmid-mediated CTX-1 and SHV-2 enzymes were highly sensitive to the action of the inhibitors clavulanic acid and sulbactam. These inhibitors protected cefotaxime from hydrolysis by these enzymes. Both CTX-1 and SHV-2 lacked activity against the cephamycins, cefoxitin, latamoxef (moxalactam) and cefotetan. The CTX-1 and SHV-2 enzymes had a low activity against oxacillin and were not sensitive to chloride ions. Thus, they were not related to the OXA type beta-lactamases. For the third-generation cephalosporins the rates of hydrolysis were high and thus bore no relation with those observed for the other presently-known beta-lactamases, with perhaps the exceptions of those produced by K. oxytoca. Imipenem was very resistant to the action of these CTX-1 and SHV-2 beta-lactamases.

Transferable resistance to third-generation cephalosporins in clinical isolates of Klebsiella pneumoniae: identification of CTX-1, a novel beta-lactamase

Approximately 10% (89 isolates) of Klebsiella pneumoniae isolated in 1985 from patients in intensive care units in Clermont-Ferrand exhibited a complex resistance phenotype towards antibiotics. They were resistant to amino-, carboxy- and ureidopenicillins, aminoglycosides (except gentamicin), chloramphenicol, sulphonamides, tetracyclines and, most importantly, to cephalosporins (except cefoxitin and latamoxef) and to aztreonam. The metabolic profile of fifty isolates was identical and seven were selected for further study. All the resistance characters in these isolates were transferable to Escherichia coli by conjugation and were lost en bloc after treatment with ethidium bromide. Agarose gel electrophoresis of crude lysates of the wild types and their transconjugants indicated that the multiple resistances were mediated by a 95kb plasmid, pCF04. The seven isolates selected for study and their corresponding transconjugants, constitutively produced a plasmid-mediated beta-lactamase with a pI of 6.3 that was much more active against third-generation cephalosporins than against cephalothin. The substrate profile and the isoelectric-focusing behaviour of this enzyme differed from those of other known plasmid-mediated beta-lactamases, and the enzyme was designated CTX-1. A chromosomally-encoded SHV-1 (PIT-2) penicillinase (pI 7.7) was also present in the seven K. pneumoniae isolates but did not transfer. Resistance to aminoglycosides in the K. pneumoniae isolates was due to synthesis of a 6'-aminoglycoside acetyltransferase type IV. Our data indicate an epidemic of antibiotic multiply-resistant strains of K. pneumoniae producing a new beta-lactamase.

[Effects of beta-lactamases on the antibacterial activity of carumonam and aztreonam against Klebsiella sp. in comparison with 4 other beta-lactams]

Carumonam and aztreonam are two similar monocyclic beta lactam antibiotics. We have studied their antibacterial activities on Klebsiella, in comparison with cefotaxime, cefoxitin, cefotetan and imipenem. In the case of K. pneumoniae (53 strains) the antibacterial activities of the two monobactams are very similar. On the contrary, with K. oxytoca (22 strains) carumonam is significantly more active. This situation seems to be justified by an improved stability of carumonam to beta lactamases. In addition, the antibacterial activities of imipenem and of cephamycins remain quite constant within all the strains. Then the antibacterial activity of cefotaxime is fluctuant, which is in relation with a clear susceptibility to the Klebsiella beta lactamases.

[Enzymologic aspect of piperacillin combinations]

Like all penicillins, piperacillin exhibits some susceptibility to beta-lactamases of the penicillinase type, including those produced by Staphylococcus aureus and the TEM, OXA and CARB enzymes isolated from Gram-negative bacilli. Piperacillin is very slightly hydrolyzed by cephalosporinases, which makes it similar to 3rd generation cephalosporins. When tested with Enterobacter cloacae GN 5797 and Pseudomonas aeruginosa NTC 8303, two strains which produce inducible cephalosporinases, piperacillin had moderate inductive activity compared to cefoxitin, a potent inducer. Induction was very low with Enterobacter, but the drug was slightly more sensitive to Pseudomonas. Inhibition of this type of beta-lactamase synthesis was very strong when piperacillin was combined with amikacin and weaker when it was combined with pefloxacin. The piperacillin-amikacin combination prevented the development of piperacillin-resistant mutants of Enterobacter and Pseudomonas and, probably, of all Gram-negative bacilli. In our tests, the piperacillin-pefloxacin combination was of interest only against Enterobacter, and probably against all enterobacteria, since Pseudomonas mutants that resist pefloxacin are fairly easily obtained in vitro.

Beta-lactamase stability of imipenem

The beta-lactamase stability and interactions of imipenem were analysed in comparison with those of cefazolin, cefuroxime, cefoxitin, cefotaxime, ceftazidime, mezlocillin, piperacillin and penicillin G for a set of representative beta-lactamases. These enzymes included penicillinases such as those obtained from Staphylococcus aureus, Escherichia coli and other Enterobacteriaceae (TEM-1 and similar enzymes) (group A); cephalosporinases produced by Esch. coli (Amp C type), Serratia liquefaciens, Enterobacter cloacae, Pseudomonas aeruginosa (group B); and beta-lactamases produced by Klebsiella spp., Proteus vulgaris and Bacteroides fragilis and with a high hydrolytic activity for the newer cephalosporins (group C). Enzymes of group A were demonstrated to be highly active against penicillins and also against the early cephalosporins; enzymes of group B showed hydrolytic activity for all other tested compounds, including the newer cephalosporins and cephamycins, but not imipenem, whereas enzymes of group C were highly active against the new cephalosporins but not against cephamycins and imipenem. In conclusion, imipenem shows a moderate affinity for all these enzymes but no detectable hydrolysis.

Sulbactam: biochemical factors involved in its synergy with ampicillin

Sulbactam is a time-dependent irreversible inhibitor of various beta-lactamases by reversible formation of a Michaelis-type enzyme-inhibitor complex and progressive evolution of this complex into inactivated protein(s). This process is either irreversible (true inactivation) or quasi-irreversible (stable acyl-enzyme). In this way, sulbactam efficiently protects ampicillin from degradation by beta-lactamases. Sulbactam itself exhibits a moderate antibacterial activity that is related to an affinity for the penicillin-binding proteins of various bacterial strains, which is similar to the affinity of penicillins such as ampicillin. However, sulbactam binding differs according to the bacterial species involved. In strains producing either low levels of beta-lactamase or none at all, a synergistic effect, minor but not negligible, can be observed when sulbactam is associated with a beta-lactam antibiotic with a complementary affinity for the target sites.

[Interactions of ceftriaxone with beta-lactamases including those which hydrolyze cefotaxime]

As it occurs with most of 3rd generation cephalosporins, ceftriaxone has few, if any, interactions with penicillinase-type beta-lactamases, such as TEM-1, TEM-2 or PIT-2. These poor interactions are characterized by an extremely low hydrolysis, associated to a poor affinity of these compounds for the penicillinases. Conversely, ceftriaxone, as cefotaxime, shows a high affinity for chromosomally-mediated cephalosporinases (indole-positive Proteus, Enterobacter, Pseudomonas...), which is characterized by Ki values ranging from about 0.05 to 1 microM. Within these beta-lactamases, the hydrolysis of ceftriaxone, as that of cefotaxime, is always low, but significant. Then few beta-lactamases are able to hydrolyze more efficiently cefotaxime, as cefuroxime, such as those produced by P vulgaris and K oxytoca. Within these enzymes, ceftriaxone is also hydrolyzed, in a way quite similar to that of cefotaxime.

[Klebsiella oxytoca beta-lactamases: study of their action on 3d-generation cephalosporins]

Indole-positive Klebsiella pneumoniae or K. oxytoca are usually resistant to penicillins as a result of the production of a chromosomally-mediated beta-lactamase with a low level of synthesis (specific activity approximately 50 to 100 mU/mg). Although most strains are susceptible to the majority of cephalosporins, some strains exhibit resistance to cephalosporins including third-generation drugs. These resistant strains produce a chromosomally-mediated beta-lactamase with a high level of synthesis (specific activity approximately 5,000 mU/mg or higher). Four beta-lactamases have been identified on the basis of their isoelectric points: pI = 5.5, 5.7, 6.0 and 6.3; nevertheless they have similar kinetic constants, and are inhibited by clavulanic acid. These enzymes hydrolyze most third-generation cephalosporins, in the following order of decreasing velocities: cefoperazone, ceftriaxone, cefotaxime, cefodizime, cefpirome; ceftazidime, and cefoxitin, cefotetan, latamoxef, cephamycins which are totally resistant to these enzymes.

Timentin and beta-lactamases

Ticarcillin is resistant to the action of cephalosporinases, which explains its biological activity on a large number of bacterial species, including cephalosporinase-producing Enterobacteriaceae and Pseudomonas aeruginosa. Nevertheless, its antibacterial activity is often limited by the action of some beta-lactamases, mostly plasmid-mediated penicillinases. Clavulanic acid by itself has poor antibacterial activity, but its most important property is to inhibit and inactivate beta-lactamases. The inhibitory properties of clavulanic acid were studied on a large number of beta-lactamases. The penicillinases produced by Staphylococcus aureus, the plasmid-mediated beta-lactamases such as the TEM-type, the chromosomally-mediated penicillinases from Klebsiella pneumoniae and other closely-related beta-lactamases, and a few chromosomally-mediated cephalosporinases, such as that produced by Proteus vulgaris, are powerfully inhibited by clavulanic acid. The plasmid-mediated penicillinases of OXA type and most of the chromosomally-mediated cephalosporinases, such as that produced by Escherichia coli (Amp C), are less or poorly inhibited. Moreover, clavulanic acid has some cephalosporinase-inducing properties. These properties are in good agreement with the bacteriological properties of Timentin.

Affinity of cefmenoxime for beta-lactamases: an analysis

The interactions of cefmenoxime with beta-lactamases in comparison with cefotaxime, moxalactam, cefoperazone, and ceftazidime have been determined. On-line computerized microacidimetry allowed determination of the affinity of these compounds with the enzymes, which was characterized by Km values. The beta-lactamases that were used were two cephalosporinases and one penicillinase. Within these data, the cephalosporins could be classified into three groups: (1) those with high affinity for the cephalosporinases and very poor affinity for the penicillinase (cefmenoxime, cefotaxime, and moxalactam); (2) those with moderate affinity for the cephalosporinases and very poor affinity for the penicillinase (ceftazidime); (3) those with poor affinity for all enzymes (cefoperazone). In the case of the penicillinase (TEM-1), only cefoperazone was subject to some hydrolysis.